Recently, an airbag system is introduced in a motorcar in order to reduce a shock of a collision to the human body. In such an airbag system, an airbag is inflated in response to a trigger signal supplied from a collision detecting apparatus.
A conventional vehicle collision detecting apparatus includes an acceleration sensor for detecting an acceleration of a motorcar, an integrator for integrating an acceleration in a predetermined range, and a comparator for comparing the integrated acceleration with a predetermined threshold value. The comparator supplies a trigger signal to an airbag driver circuit, when the integrated value is higher than the threshold value.
According to the conventional vehicle collision detecting apparatus, a collision of a vehicle is detected in accordance with the integrated acceleration indicating a minute change of a car velocity. However, a collision of a vehicle is not detected with a high precision, because the integrated acceleration includes much noise.